Modeling of autothermal methane steam reforming: Comparison of reactor configurations

Murmura, Maria Anna; Diana, M.; Spera, Romina; Annesini, Maria Cristina

doi:10.1016/j.cep.2016.08.019

Cited by 32 publications

(14 citation statements)

References 30 publications

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“…Clearly, the likelihood of hotspot generation or runaway reactions taking place in the VTMR is significantly reduced through the modulation of O2 permeation. Equivalent observations were reported in studies of similar reactor concepts for the autothermal reforming of methane [21] and the selective oxidation of o-xylene to phthalic anhydride [2]. A maximum temperature difference of about 200 K is observed between the two configurations for the simulated conditions at the end of the reactor.…”

Section: Non-isothermal Performancesupporting

confidence: 54%

“…To decrease secondary C2 oxidation, Godini et al [6] used a modified porous membrane with decreasing O2 permeation, reporting a 25.8 % C2 yield and 66 % C2 selectivity. The use of distributed or staged O2 feeding has also been considered for other processes, such as autothermal steam reforming of methane [19][20][21][22], although primarily aiming at optimal temperature control. Aworinde et al [2] further showed selectivity improvements via the simultaneous modulation of O2 and coolant temperature for the preferential oxidation of o-xylene to phthalic anhydride.…”

Section: Accepted M M a N U mentioning

confidence: 99%

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Influencing selectivity in the oxidative coupling of methane by modulating oxygen permeation in a variable thickness membrane reactor

Onoja

Wang

Kechagiopoulos

2019

Chemical Engineering and Processing - Process Intensification

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The Oxidative Coupling of Methane (OCM) has been considered for years as a promising alternative for the production of higher hydrocarbons, namely ethane and ethylene. Nonetheless, OCM's inherent conversion-versus-selectivity limitations have not allowed till now for economical C2 yields to be achieved. Reactor engineering studies guided by a detailed mechanistic description of the reaction can directly contribute to obtaining an understanding of these limitations. In this work, a Variable Thickness Membrane Reactor (VTMR) is proposed, wherein O2 permeation along the reactor is modulated, aiming at maximizing C2 selectivity. 1D and 2D reactor simulations are carried out to compare the performance of this reactor to conventional co-feed Packed Bed Reactors (PBR) and Membrane Reactors without variable thickness (MR). Particular attention is given on the impact of gas phase reactions on C2 selectivity, while the effect of surface exchange kinetics on both sides of the membrane and bulk diffusion of O2 across the membrane is discriminated. When identical operating conditions (T = 1073 K, P = 1 atm, Space time = 7.85 s) and reactor geometry (Length = 0.1 m, Diameter = 0.01 m) were evaluated, the optimization performed of the VTMR configuration achieved a C2 selectivity of 67.26 %, in comparison to 47.86 % and 29.87 % for the MR and PBR, respectively, highlighting the potential of the concept.

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Section: Non-isothermal Performancesupporting

confidence: 54%

Section: Accepted M M a N U mentioning

confidence: 99%

Influencing selectivity in the oxidative coupling of methane by modulating oxygen permeation in a variable thickness membrane reactor

Onoja

Wang

Kechagiopoulos

2019

Chemical Engineering and Processing - Process Intensification

View full text Add to dashboard Cite

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“…These kinetic models are commonly used by many researchers today for the reforming processes that involve steam reforming, dry reforming, and partial and complete oxidation, such as tri and autothermal reforming (Eqs. (7)- (11)) [18,[22][23][24][25][26][27]:…”

Section: Reaction Scheme and Kineticsmentioning

confidence: 99%

“…To model the flow and reactions of the reforming process along the packed-bed reactor, Eqs. (25) and (26) were solved simultaneously:…”

Section: Governing Equationsmentioning

confidence: 99%

Kinetic and CFD Modeling of Exhaust Gas Reforming of Natural Gas in a Catalytic Fixed‐Bed Reactor for Spark Ignition Engines

et al. 2020

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Fuel reforming is an attractive method for performance enhancement of internal combustion engines fueled by natural gas, since the syngas can be generated inline from the reforming process. In this study, 1D and 2D steady‐state modeling of exhaust gas reforming of natural gas in a catalytic fixed‐bed reactor were conducted under different conditions. With increasing engine speed, methane conversion and hydrogen production increased. Similarly, increasing the fraction of recirculated exhaust gas resulted in higher consumption of methane and generation of H2 and CO. Steam addition enhanced methane conversion. However, when the amount of steam exceeded that of methane, less hydrogen was produced. Increasing the wall temperature increased the methane conversion and reduced the H2/CO ratio.

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“…Traditionally, ATR is carried out in reactors formed by a combustion chamber and a catalytic section; in this configuration all the heat is released immediately after the inlet section and a temperature peak is observed, with problems in terms of reactor control and resistance of catalyst and construction materials. Two alternative configurations have been considered [14]: in the first one the two reactions (the exothermic catalytic combustion providing the heat to drive the endothermic steam reforming) are carried out in two spatially separated chambers, with a thin wall between the two chambers which is the only resistance to heat transfer; in the second one, only part of the oxygen is mixed with the SR feed, whereas the remaining portion is distributed along the reaction axis. In both case smooth thermal profiles are obtained.…”

mentioning

confidence: 99%

Scale Down of Reforming Processes for Hydrogen Production from Renewable Sources

Annesini¹

2017

World Congress on Mechanical, Chemical, and Material Engineering

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Hydrogen has attracted much interest as energy carrier, both as feed for fuel cells or as an environmentally friendly fuel for automotive and a transition from a fossil fuel to a hydrogen-based economy has been forecasting for the 2050s. Nowadays, major issues concerning a wide use of hydrogen are related to the lack of a proper H2 grid and problems related to hydrogen storage (mainly due to the low energy density and safety issues). Scale down of the production, allowing a decentralized hydrogen production (close to the end-user), or production on-board of vehicles can bypass these problems.Traditionally, hydrogen is widely used in the chemical industry and it is mainly produced by natural gas (NG) reforming, an endothermic process that demands a large heat input and, due to the equilibrium limitations, high temperature to obtain large conversion. Furthermore, this process requires the integration of different units (the reformer itself, the water gas shift reactor and separation units to recover hydrogen)The challenges for scale down are mainly related to the success in reducing the operating temperature, simplifying the reforming process with integrated units and using liquid feedstock. The use of renewable sources both as feedstock for the reforming and to supply the energy required for endothermic process is also advisable for process sustainability.If reforming is carried out at moderate temperatures (400-500°C), a significant gain in material costs can be achieved; furthermore, at these temperatures, concentrating solar power equipment can be used as energy source for sustaining the hydrogen-producing endothermic reaction, thus reducing the carbon footprint of the process. On the other hand, thermodynamics limit the conversion at 30-40%. Therefore, two approaches have been considered.The first one, carried out with the financial support of the METISOL project of the Italian Environment Ministry, is to exploit the possibility to produce an enriched methane mixture (EM) with a hydrogen content between 10 -30% v/v; such a mixture can be used as feedstock in the traditional natural gas IC engines to improve the engine efficiency and to reduce the emission of green house gases; furthermore EM can be stored and distributed by the standard NG storage systems or medium pressure grid [1]. Indeed if the process is aimed to EM production, hydrogen does not have to be separated from unreacted CH4, but separation units to remove carbon dioxide are required [2].The second one is to use membrane reactors (MR), comprising a palladium or palladium-silver membrane, to overcome the thermodynamic limitation by separating hydrogen from the reacting mixture. Indeed, these membranes have an infinite selectivity for hydrogen and two goals can be achieved: a) the hydrogen separation shifts the reaction towards the product and allow to reach high conversion even at low temperature, b) hydrogen with a very high degree of purity, as required for fuel cells, is obtained. These considerations are at the basis of the CoMETHy (Compact M...

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Modeling of autothermal methane steam reforming: Comparison of reactor configurations

Cited by 32 publications

References 30 publications

Influencing selectivity in the oxidative coupling of methane by modulating oxygen permeation in a variable thickness membrane reactor

Influencing selectivity in the oxidative coupling of methane by modulating oxygen permeation in a variable thickness membrane reactor

Kinetic and CFD Modeling of Exhaust Gas Reforming of Natural Gas in a Catalytic Fixed‐Bed Reactor for Spark Ignition Engines

Scale Down of Reforming Processes for Hydrogen Production from Renewable Sources

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